1. Field of the Invention
The present invention relates to a single radiant tube burner, and more specifically, to a full time regenerative type single radiant tube burner.
2. Description of the Related Art
Generally, a combustor such as a burner, etc., is a device that combusts fuel and air that are injected at an appropriate mixing ratio, transfers heat energy generated upon combusting to other media to melt the media or change the temperature of the media, and is used to convert heat energy into electric or kinetic energy.
The combustor or the burner, etc., should implement combustion reaction in an industrial furnace and the optimization of electro thermal characteristic and achieve the optimal temperature in the industrial furnace.
In addition, the ideal combustor or burner, etc., should be easy to handle and be safe, be in a work environment that is harmless to a person, and be maintained at high efficiency while minimizing emissions of heat, gas, fluid, pollutant, etc.
In other words, it is a major object to develop the combustor or the burner, etc., which can be operated at high efficiency and acquire flame stabilization while minimizing the amount of NOx (nitrogen oxide) emitted upon combusting, which are challenges to be pursued in the future.
However, these are ideal challenges and are still not completely solved.
In other words, the combustor in the related art excessively emits the amount of NOx (nitrogen oxide) upon combusting, which is a level of a risk that is harmful to an environment or a human body.
Therefore, many researches on the development of the combustor or the burner, etc., for generating the low NOx (nitrogen oxide) have been long performed at home and abroad and the non-equilibrium combustion method such as a multi-stage combustion method or a lean/rich combustion method has been mainly researched.
Further, there is an exhaust gas re-circulating method that reduces NOx by lowering the flame maximum temperature the combustion exhaust gas by using the internal circulation manner or the external circulation manner and there is a technology that uses a selective catalytic reduction (SCR) apparatus and a selective non-catalytic reduction (SNCR) apparatus as a post-processing method.
In addition, several attempts, such as a technology of using a reburning effect by the stepwise supply of fuel injection, the temperature uniformity by surface/catalyst combustion, etc., have been performed, which is being continuously developed today.
However, it is not easy to develop the energy saving type low NOx (nitrogen oxide) combustor that has the stabilization of flame, does not almost generate the unburned carbon, and has the industrial furnace system of high heat efficiency.
The reason is that the flame temperature to reduce the NOx is lowered and thus the reduction of the energy efficiency is evitable.
1) The non-equilibrium combustion method and 2) the exhaust gas re-circulating combustion method, which are related to the present invention, among the existing researched and developed NOx (nitrogen oxide) suppressing methods will be sequentially described below.
1) Non-Equilibrium Combustion Method
As the non-equilibrium combustion method, there are an air 2 state supply combustion method and a bias combustion method. The methods are the same in that they control the supply ratio of air for combusting to suppress the generation of the NOx (nitrogen oxide).
Reviewing the generation ratio of the NOx (nitrogen oxide) according to the combustion, a part where the generating point is highest is generated in a mixing ratio having excellent combustion efficiency by a predetermined mixing between fuel and air.
In other words, the heat efficiency is highest but the generation amount of the NOx (nitrogen oxide) reaches the highest point, at the mixing ratio, which is antinomic.
Therefore, the non-equilibrium combustion method supplies air to be out of the mixing ratio between fuel and air to maximally generate the NOx (nitrogen oxide).
Describing in more detail, the air 2 stage supply combustion method is a combustion method that separates and supplies air at primary and secondary steps.
The air 2 stage supply combustion method is a method that at a primary step, supplies air, at smaller amount than a mixing amount of air where the generation amount of the NOx (nitrogen oxide) reaches the highest point and at secondary step, supplies a excessive amount of air to avoid the highest point where the NOx (nitrogen oxide) is wholly generated.
Of course, a method that supplies an excessive amount of air at a primary step and supplies a small amount at a secondary step can be obtained the same object.
On the other hand, the bias combustion method is a method that implements two areas, that is, a small amount of air ratio area and a high amount of air ratio area to be adjacent to each other.
In other words, there may be, for example, a bias tip, etc., that largely separates one burner nozzle in the type operated at a generally appropriate air ratio and small separates the other one burner nozzle by combusting one of two burners at a low air ratio and combusting the other burner at high air ratio.
As a result, the method makes the air distribution uneven to avoid the peak value the generation of the NOx (nitrogen oxide).
2) Exhaust Gas Re-Circulating Method
The exhaust gas re-circulating method is a method for suppressing the generated NOx that re-circulates the gas combusted once and combusts again, to increase the volume of the combustion gas and lower the temperature of flame.
At this time, when the exhaust gas is re-circulated, the exhaust gas can be circulated in the air for combustion but can be re-circulated in the supplied fuel.
However, as the exhaust gas re-circulating method, there are an internal type and an external type. The external type is a type that some of the combusted and emitted exhaust gas is mixed in an injection fuel pipe or an air pipe for combustion and supplies it to the combustor again.
On the other hand, the internal type is a type that re-circulates the exhaust gas in the furnace.
Therefore, the external type and the internal type reduces the injection amount of air for combustion to re-circulate the exhaust gas by air for recombustion.
Of course, this reduces the flame temperature and thus, the generation of the NOx (nitrogen oxide) is reduced.
As a result, 1) the non-equilibrium combustion method or 2) the exhaust gas re-circulating method controls the injection amount of air that is necessary for combustion to avoid the mixing ratio at which the generation of the NOx (nitrogen oxide) is a peak value.
It can be considered that the method for suppressing the generation of the NOx (nitrogen oxide) is already emerged. However, when the method is applied to the combustor or the burner, etc., there is still the problem of the improvement of heat efficiency.
Therefore, a method for simultaneously obtaining the effect of suppressing the nitrogen oxide by applying the exhaust gas re-circulating method to the burner, etc., has been sought.
In other words, in order to prevent the high-temperature exhaust gas generated by the flame from being uselessly emitted to the air, it re-circulates the exhaust gas but collects the heat energy of the exhaust gas in a regenerator to be reused.
The burner that is in the high-temperature state by accumulating the heat energy in the regenerator can be combusted in the atmosphere of low oxygen concentration, such that it can suppress the generation of the NOx (nitrogen oxide) while naturally avoiding the peak point.
Further, the industrial furnace, which does not perform the existing regeneration, is partitioned into a high-temperature area and a low-temperature area when flame is emitted from the burner.
In other words, the high-temperature and clear flame zone locally exists in some areas.
On the other hand, the burner, which always maintains the high-temperature state due to the regeneration, is not partitioned into the high-temperature area and the low-temperature area when flame is emitted and long forms the flame and is combusted in the state where the flame temperature is uniform to some degree.
This is extended until it reaches the non-flame to suppress the generation of the NOx (nitrogen oxide) and obtains the effect that can effectively manage the wasted heat energy.
As described above, the problem of the embodiment (burner) will be described by reviewing the burner that regenerates and reuses the heat energy in the burner by applying the exhaust gas re-circulating method.
First, there is a twin regenerative type burner system 10 where combustors A and B such as a burner, etc., for combustion are installed to be opposite left and right, as shown in FIG. 1.
In other words, the two combustors A and B, which faces each other, are provided with separate regenerators C and D.
Therefore, when the combustor A emits firepower and emits the high-temperature exhaust gas, waste heat energy is accumulated in a regenerator D that is attached to the combustor B.
This state is maintained for about 20 to 80 seconds and then, a regenerator C, which is attached to the combustor A facing the combustor B that emits firepower accumulates heat.
In other words, the combustors are alternately operated and when one combustor emits firepower, the other accumulates heat energy.
Second, FIG. 2 shows a honey comb type regenerative combustion system 20 that is used for the same purpose as the above-mentioned twin regenerative burner system, wherein the honey comb type regenerative combustion system 20 has combustors E and F that are installed to be parallel left and right to emit firepower and accumulates the emission heat of the exhaust gas in regenerators G and H.
Third, FIG. 3 shows a radiant tube type regenerative burner system that is used for the same purpose as the above-mentioned burner system, wherein the radiant tube type regenerative burner system has the combustors I and J such as the burner for combustion that are installed to be opposite to both ends of the radiant tube and have the regenerative body therein.
In this system, when the combustor I emits firepower and emits the high-temperature exhaust gas, the heat energy of the high-temperature exhaust gas, which is transferred through the radiant tube is accumulated in the regenerator D included in the combustor J.
This state is maintained for a predetermined time and then, when the combustor B emits firepower, the combustor I opposite thereto accumulates the heat energy.
In other words, the combustors are alternately operated and when one combustor emits firepower, the other accumulates heat energy.
However, the regenerative combustor necessarily needs two combustors and therefore, the manufacturing cost thereof is increased.
The combustor less than 1000 KW, which has a small combustion amount, is difficult to apply since the application cost of the system is greatly increased as compared with combustion amount
In addition, it is difficult to install the burner in the combustion furnace having a narrow installation space.
In addition, the twin regenerative type burner system, which should be installed in two, the honey comb type regenerative combustion system, and the radiant tube type system have a large volume, such that they has a spatial restriction.
In other words, it is difficult to apply to a heat treatment furnace or a chemical reaction furnace such as a carburizing furnace that the maximum size and number of the burner are limited.